I have Yoshi's Island DS, and am currently half-way through world 5. Pretty good stuff so far (and some very challenging levels in there), but as mentioned earlier this game is very reminiscient of the original Yoshi's Island, not that that's a bad thing.
Pros:
- Same solid sidescrolling gameplay
- Throwing eggs feels the same (thank God)
- Changing babies to achieve different goals is usually fun, clever, and well-executed
- Art style is different enough to feel fresh but not too different
Cons:
- I don't like the music as much as the music in Yoshi's Island... just not as catchy and upbeat
- THEY TOOK OUT ITEMS!! wtf. On the one hand, this makes the levels a lot harder because you actually have to finish with 30 stars to get 100%... can't just whip out the "+20 stars" item. However, I don't understand why they had to do this. In the first game, you only had to get to the end with all 30 stars on the boss levels... now you have to do it with every level. On the other hand, this adds an extra (albeit annoying) degree of challenge... so if you're into that, move this to the "pros" list.
- You can't push Chomp Rocks at the speed of light and gain ultra momentum, they only go a very slow top speed (minor complaint)
- There is the occasional "Donkey Kong 64" moment when you see an item you can't get, realize you have the wrong baby and it's too late to change to the right one. VERY IRRITATING when this happens since every level has a character coin and you have to have the right baby to collect it. Having the wrong baby at the time usually means you will have to play through the whole level again just to get it.
- Maybe it's just me but it seems like there are lots more "points of no return" in this game than the original. e.g. You go to the next room, and you can't go back... or you fall down a cliff and can't get back up once you're down there. Again, not a huge deal but it gets irritating when you realize you're not going to get 100% because you saw two ways to go and chose the wrong way.
I haven't beaten the whole game yet but what I've seen so far is good overall and I'd say it's definitely worth a purchase for any fan of the original.